The main reservoirs in Brazil’s deepwater basins consist of soft, high-porosity sandstones, many of which are highly faulted and fractured. Under lithostatic pressure from overlying rocks, most of these faults have achieved relative tectonic stability for millions of years. However, even a slight alteration of the stress field within a hydrocarbon reservoir, or its overburden, can trigger dormant faults to slip. Rapid pressure depletion through production and pressure changes, due to water injection, may be sufficient to disturb the in-situ stress regime and reactivate faults.